I don't understand....
If I uninstall 2.7, is the reg information going to be maintained in the registry ?
(I assume by remove, you mean using add/remove programs)
Do I have to be sure of anything when I go to install v3?

Here are steps I copied several months ago from a thread on this web site.

1. Uninstall v.3.0.621 (or whatever version you have) from Control Panel -> Add/Remove programs . Be patient , uninstall may take longer than expected.
2. Reboot the computer when prompted
3. Download fresh new Eset NOD32. Make sure you choose the correct version.
4. Delete manually this folders:- C:\Documents and Settings\All users\Application data\Eset
4a. Also delete folders from Program Files
5. Reinstall your ESET NOD32 with the file you just downloaded . Use Typical install.

Admittedly, I have only reinstalled NOD32 once; that occurred when my system got infected by a Trojan last winter and obliterated my NOD32 program at that time. Can't say I've been that impressed. In any event, this may be a good opportunity for others more experienced with the uninstall/reinstall process to chime in and either agree with or edit the above steps.

By the way needlicense, I don't know if you've been following the attached thread today...but you just may want to keep 2.7 installed. It seems to withstand the seemingly sloppily-written ESET security updates that have been crippling systems. And apparently it's not the first time this has happened in recent months.https://www.wilderssecurity.com/showthread.php?p=1315202#post1315202

yes, doodler, thanks.
I've been watching that.
Right now, nod32krn.exe, when launched, exits (?) about 15 seconds after it's started. Is it a virus or something killing it? Or is there something wrong with the interaction between the current version and the latest vista update.

It seems (?) like problems started after my system re-booted after the latest Vista update. At least that's when I noticed it.